One interpretation of this deceptively simple poem is that the narrator of "Dover Beach" has lost his faith in humanity. He sees the ocean as symbolic of ebb and flow of human events, influenced by forces beyond human control, as the sea is moved by the pull of the moon. He says that:

The Sea of Faith

Was once, too, at the full, and round earth’s shore

Lay like the folds of a bright girdle furled.

But now I only hear

Its melancholy, long, withdrawing roar....

This could be faith in god, as well, but the final stanza suggests that he wants his lover to keep faith with him. The world is confusion, he says, and when all is said and done, we only have each other.

The world is just the world and is insensible to human desire and pleasure and pain, just like the sea, "And we are here as on a darkling plain / Swept with confused alarms of struggle and flight, / Where ignorant armies clash by night." This is a reference to battles, but the sea--waves on sand, crashing forever--is his metaphor.